Prosthetic replacements for the arthritic knee are currently in a stage of evolution. A variety of prostheses have been designed along with variations of each type which are being used clinically across the country. The purpose of this project is to evaluate the mechanical aspects and durability of replacement prostheses in the laboratory and simultaneously attempt to construct a prosthesis which will have wider application and increased reliability over those currently available. In carrying out this work, a knee joint simulator has been constructed and currently is being used for testing prostheses in cadaver knee joints. Additional studies are being carried out defining the mechanical characteristics of the knee joint, both in clinical situations and in cadaver knee joints. A model for a prosthetic knee joint designed in this laboratory has gone through provisional testing and is under construction. The knee joint should be available for further testing and clinical studies during the coming year.